As a capacitor meeting uses where high energy density and high power density properties are required, attention has been recently paid to an accumulator device what is called a hybrid capacitor with the principles of electricity accumulation in the lithium ion secondary battery and the electric double layer capacitor combined. This accumulator device is an organic electrolyte capacitor having a negative electrode composed of a carbonaceous material capable of occluding and deoccluding lithium ions, by which a high energy density is achieved by lowering the potential thereof by causing lithium ions occluded and supported (hereinafter also referred to as “doped”) in the carbonaceous material in advance by a chemical method or electrochemical method (see, for example, Patent Literature 1 and Patent Literature 2).
As such accumulator devices, are known that of a wound-type which has an electrode unit configured by winding an electrode stack, which is obtained by stacking a positive electrode and a negative electrode on each other through a separator capable of being impregnated with an electrolytic solution, from one end thereof, that of a laminated-type which has an electrode unit composed of an electrode stack obtained by alternately stacking a plurality of positive electrodes and a plurality of negative electrodes on each other through a separator capable of being impregnated with an electrolytic solution, and the like. In addition, as outer containers for housing the electrode unit, are known that of a metallic can shape (see Patent Literature 3), that composed of a laminate film having an aluminum layer as an intermediate layer (see Patent Literature 4), and the like. Iron, steel or the like has been used as a metallic material forming the can-shaped outer container. However, aluminum or an aluminum alloy has also been recently used from the viewpoint of weight saving of the accumulator device.